// indexContainerCache.java
// (C) 2008 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
// first published 30.03.2008 on http://yacy.net
//
// This is a part of YaCy, a peer-to-peer based web search engine
//
// $LastChangedDate: 2008-03-14 01:16:04 +0100 (Fr, 14 Mrz 2008) $
// $LastChangedRevision: 4558 $
// $LastChangedBy: orbiter $
//
// LICENSE
// 
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

package de.anomic.kelondro.text;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;

import de.anomic.kelondro.blob.HeapReader;
import de.anomic.kelondro.blob.HeapWriter;
import de.anomic.kelondro.order.CloneableIterator;
import de.anomic.kelondro.order.Base64Order;
import de.anomic.kelondro.order.ByteOrder;
import de.anomic.kelondro.util.Log;
import de.anomic.kelondro.index.Row;
import de.anomic.kelondro.index.RowSet;

public final class ReferenceContainerCache implements Iterable<ReferenceContainer>, Index {

    private final Row payloadrow;
    private SortedMap<String, ReferenceContainer> cache;
    
    /**
     * opens an existing heap file in undefined mode
     * after this a initialization should be made to use the heap:
     * either a read-only or read/write mode initialization
     * @param payloadrow
     * @param log
     */
    public ReferenceContainerCache(final Row payloadrow) {
        this.payloadrow = payloadrow;
        this.cache = null;
    }
    
    public Row rowdef() {
        return this.payloadrow;
    }
    
    public void clear() {
        if (cache != null) cache.clear();
        initWriteMode();
    }
    
    public void close() {
    	this.cache = null;
    }
    
    /**
     * initializes the heap in read/write mode without reading of a dump first
     * another dump reading afterwards is not possible
     */
    public void initWriteMode() {
        this.cache = Collections.synchronizedSortedMap(new TreeMap<String, ReferenceContainer>(new ByteOrder.StringOrder(payloadrow.getOrdering())));
    }
    
    /**
     * restore a heap dump: this is a heap in write mode. There should no heap file
     * be assigned in initialization; the file name is given here in this method
     * when the heap is once dumped again, the heap file name may be different
     * @param heapFile
     * @throws IOException
     */
    public void initWriteModeFromHeap(final File heapFile) throws IOException {
        Log.logInfo("indexContainerRAMHeap", "restoring dump for rwi heap '" + heapFile.getName() + "'");
        final long start = System.currentTimeMillis();
        this.cache = Collections.synchronizedSortedMap(new TreeMap<String, ReferenceContainer>(new ByteOrder.StringOrder(payloadrow.getOrdering())));
        int urlCount = 0;
        synchronized (cache) {
            for (final ReferenceContainer container : new heapFileEntries(heapFile, this.payloadrow)) {
                // TODO: in this loop a lot of memory may be allocated. A check if the memory gets low is necessary. But what do when the memory is low?
                if (container == null) break;
                cache.put(container.getWordHash(), container);
                urlCount += container.size();
            }
        }
        Log.logInfo("indexContainerRAMHeap", "finished rwi heap restore: " + cache.size() + " words, " + urlCount + " word/URL relations in " + (System.currentTimeMillis() - start) + " milliseconds");
    }
    
    /**
     * this is the new cache file format initialization
     * @param heapFile
     * @throws IOException
     */
    public void initWriteModeFromBLOB(final File blobFile) throws IOException {
        Log.logInfo("indexContainerRAMHeap", "restoring rwi blob dump '" + blobFile.getName() + "'");
        final long start = System.currentTimeMillis();
        this.cache = Collections.synchronizedSortedMap(new TreeMap<String, ReferenceContainer>(new ByteOrder.StringOrder(payloadrow.getOrdering())));
        int urlCount = 0;
        synchronized (cache) {
            for (final ReferenceContainer container : new blobFileEntries(blobFile, this.payloadrow)) {
                // TODO: in this loop a lot of memory may be allocated. A check if the memory gets low is necessary. But what do when the memory is low?
                if (container == null) break;
                //System.out.println("***DEBUG indexContainerHeap.initwriteModeFromBLOB*** container.size = " + container.size() + ", container.sorted = " + container.sorted());
                cache.put(container.getWordHash(), container);
                urlCount += container.size();
            }
        }
        // remove idx and gap files if they exist here
        HeapWriter.deleteAllFingerprints(blobFile);
        Log.logInfo("indexContainerRAMHeap", "finished rwi blob restore: " + cache.size() + " words, " + urlCount + " word/URL relations in " + (System.currentTimeMillis() - start) + " milliseconds");
    }
    
    public void dump(final File heapFile) throws IOException {
        assert this.cache != null;
        Log.logInfo("indexContainerRAMHeap", "creating rwi heap dump '" + heapFile.getName() + "', " + cache.size() + " rwi's");
        if (heapFile.exists()) heapFile.delete();
        final HeapWriter dump = new HeapWriter(heapFile, payloadrow.primaryKeyLength, Base64Order.enhancedCoder);
        final long startTime = System.currentTimeMillis();
        long wordcount = 0, urlcount = 0;
        String wordHash;
        ReferenceContainer container;
        
        // write wCache
        synchronized (cache) {
            for (final Map.Entry<String, ReferenceContainer> entry: cache.entrySet()) {
                // get entries
                wordHash = entry.getKey();
                container = entry.getValue();
                
                // put entries on heap
                if (container != null && wordHash.length() == payloadrow.primaryKeyLength) {
                    dump.add(wordHash.getBytes(), container.exportCollection());
                    urlcount += container.size();
                }
                wordcount++;
            }
        }
        dump.close();
        Log.logInfo("indexContainerRAMHeap", "finished alternative rwi heap dump: " + wordcount + " words, " + urlcount + " word/URL relations in " + (System.currentTimeMillis() - startTime) + " milliseconds");
    }
    
    public int size() {
        return (this.cache == null) ? 0 : this.cache.size();
    }
    
    /**
     * static iterator of heap files: is used to import heap dumps into a write-enabled index heap
     */
    public static class heapFileEntries implements Iterator<ReferenceContainer>, Iterable<ReferenceContainer> {
        DataInputStream is;
        byte[] word;
        Row payloadrow;
        ReferenceContainer nextContainer;
        
        public heapFileEntries(final File heapFile, final Row payloadrow) throws IOException {
            if (!(heapFile.exists())) throw new IOException("file " + heapFile + " does not exist");
            is = new DataInputStream(new BufferedInputStream(new FileInputStream(heapFile), 1024*1024));
            word = new byte[payloadrow.primaryKeyLength];
            this.payloadrow = payloadrow;
            this.nextContainer = next0();
        }
        
        public boolean hasNext() {
            return this.nextContainer != null;
        }

        private ReferenceContainer next0() {
            try {
                is.readFully(word);
                return new ReferenceContainer(new String(word), RowSet.importRowSet(is, payloadrow));
            } catch (final IOException e) {
                return null;
            }
        }
        
        /**
         * return an index container
         * because they may get very large, it is wise to deallocate some memory before calling next()
         */
        public ReferenceContainer next() {
            final ReferenceContainer n = this.nextContainer;
            this.nextContainer = next0();
            return n;
        }

        public void remove() {
            throw new UnsupportedOperationException("heap dumps are read-only");
        }

        public Iterator<ReferenceContainer> iterator() {
            return this;
        }
        
        public void close() {
            if (is != null) try { is.close(); } catch (final IOException e) {}
            is = null;
        }
        
        protected void finalize() {
            this.close();
        }
    }

    /**
     * static iterator of BLOBHeap files: is used to import heap dumps into a write-enabled index heap
     */
    public static class blobFileEntries implements Iterator<ReferenceContainer>, Iterable<ReferenceContainer> {
        Iterator<Map.Entry<String, byte[]>> blobs;
        Row payloadrow;
        
        public blobFileEntries(final File blobFile, final Row payloadrow) throws IOException {
            this.blobs = new HeapReader.entries(blobFile, payloadrow.primaryKeyLength);
            this.payloadrow = payloadrow;
        }
        
        public boolean hasNext() {
            return blobs.hasNext();
        }

        /**
         * return an index container
         * because they may get very large, it is wise to deallocate some memory before calling next()
         */
        public ReferenceContainer next() {
            Map.Entry<String, byte[]> entry = blobs.next();
            byte[] payload = entry.getValue();
            return new ReferenceContainer(entry.getKey(), RowSet.importRowSet(payload, payloadrow));
        }
        
        public void remove() {
            throw new UnsupportedOperationException("heap dumps are read-only");
        }

        public Iterator<ReferenceContainer> iterator() {
            return this;
        }
        
        public void close() {
            blobs = null;
        }
        
        protected void finalize() {
            this.close();
        }
    }

    public synchronized int maxReferences() {
        // iterate to find the max score
        int max = 0;
        for (ReferenceContainer container : cache.values()) {
            if (container.size() > max) max = container.size();
        }
        return max;
    }
    
    public synchronized String maxReferencesHash() {
        // iterate to find the max score
        int max = 0;
        String hash = null;
        for (ReferenceContainer container : cache.values()) {
            if (container.size() > max) {
                max = container.size();
                hash = container.getWordHash();
            }
        }
        return hash;
    }
    
    public synchronized ArrayList<String> maxReferencesHash(int bound) {
        // iterate to find the max score
        ArrayList<String> hashes = new ArrayList<String>();
        for (ReferenceContainer container : cache.values()) {
            if (container.size() >= bound) {
                hashes.add(container.getWordHash());
            }
        }
        return hashes;
    }
    
    public synchronized ReferenceContainer latest() {
        ReferenceContainer c = null;
        for (ReferenceContainer container : cache.values()) {
            if (c == null) {c = container; continue;}
            if (container.lastWrote() > c.lastWrote()) {c = container; continue;}
        }
        return c;
    }
    
    public synchronized ReferenceContainer first() {
        ReferenceContainer c = null;
        for (ReferenceContainer container : cache.values()) {
            if (c == null) {c = container; continue;}
            if (container.lastWrote() < c.lastWrote()) {c = container; continue;}
        }
        return c;
    }
    
    public synchronized ArrayList<String> overAge(long maxage) {
        ArrayList<String> hashes = new ArrayList<String>();
        long limit = System.currentTimeMillis() - maxage;
        for (ReferenceContainer container : cache.values()) {
            if (container.lastWrote() < limit) hashes.add(container.getWordHash());
        }
        return hashes;
    }
    
    /**
     * return an iterator object that creates top-level-clones of the indexContainers
     * in the cache, so that manipulations of the iterated objects do not change
     * objects in the cache.
     */
    public synchronized CloneableIterator<ReferenceContainer> referenceIterator(final String startWordHash, final boolean rot, final boolean ram) {
        return new heapCacheIterator(startWordHash, rot);
    }


    public Iterator<ReferenceContainer> iterator() {
        return referenceIterator(null, false, true);
    }
    
    
    /**
     * cache iterator: iterates objects within the heap cache. This can only be used
     * for write-enabled heaps, read-only heaps do not have a heap cache
     */
    public class heapCacheIterator implements CloneableIterator<ReferenceContainer>, Iterable<ReferenceContainer> {

        // this class exists, because the wCache cannot be iterated with rotation
        // and because every indexContainer Object that is iterated must be returned as top-level-clone
        // so this class simulates wCache.tailMap(startWordHash).values().iterator()
        // plus the mentioned features
        
        private final boolean rot;
        private Iterator<ReferenceContainer> iterator;
        
        public heapCacheIterator(final String startWordHash, final boolean rot) {
            this.rot = rot;
            this.iterator = (startWordHash == null) ? cache.values().iterator() : cache.tailMap(startWordHash).values().iterator();
            // The collection's iterator will return the values in the order that their corresponding keys appear in the tree.
        }
        
        public heapCacheIterator clone(final Object secondWordHash) {
            return new heapCacheIterator((String) secondWordHash, rot);
        }
        
        public boolean hasNext() {
            if (rot) return true;
            return iterator.hasNext();
        }

        public ReferenceContainer next() {
            if (iterator.hasNext()) {
                return (iterator.next()).topLevelClone();
            }
            // rotation iteration
            if (!rot) {
                return null;
            }
            iterator = cache.values().iterator();
            return (iterator.next()).topLevelClone();
        }

        public void remove() {
            iterator.remove();
        }

        public Iterator<ReferenceContainer> iterator() {
            return this;
        }
        
    }

    /**
     * test if a given key is in the heap
     * this works with heaps in write- and read-mode
     * @param key
     * @return true, if the key is used in the heap; false othervise
     */
    public boolean hasReferences(final String key) {
        return this.cache.containsKey(key);
    }
    
    /**
     * get a indexContainer from a heap
     * @param key
     * @return the indexContainer if one exist, null otherwise
     */
    public ReferenceContainer getReferences(final String key, Set<String> urlselection) {
        if (urlselection == null) return this.cache.get(key);
        ReferenceContainer c = this.cache.get(key);
        if (c == null) return null;
        // because this is all in RAM, we must clone the entries (flat)
        ReferenceContainer c1 = new ReferenceContainer(c.getWordHash(), c.row(), c.size());
        Iterator<ReferenceRow> e = c.entries();
        ReferenceRow ee;
        while (e.hasNext()) {
            ee = e.next();
            if (urlselection.contains(ee.urlHash())) c1.add(ee);
        }
        return c1;
    }

    /**
     * return the size of the container with corresponding key
     * @param key
     * @return
     */
    public int countReferences(final String key) {
        ReferenceContainer c = this.cache.get(key);
        if (c == null) return 0;
        return c.size();
    }
    
    /**
     * delete a indexContainer from the heap cache. This can only be used for write-enabled heaps
     * @param wordHash
     * @return the indexContainer if the cache contained the container, null othervise
     */
    public synchronized ReferenceContainer deleteAllReferences(final String wordHash) {
        // returns the index that had been deleted
        assert this.cache != null;
        return cache.remove(wordHash);
    }

    public synchronized boolean removeReference(final String wordHash, final String urlHash) {
        assert this.cache != null;
        final ReferenceContainer c = cache.get(wordHash);
        if ((c != null) && (c.remove(urlHash) != null)) {
            // removal successful
            if (c.size() == 0) {
                deleteAllReferences(wordHash);
            } else {
                cache.put(wordHash, c);
            }
            return true;
        }
        return false;
    }
    
    public synchronized int removeReferences(final String wordHash, final Set<String> urlHashes) {
        assert this.cache != null;
        if (urlHashes.size() == 0) return 0;
        final ReferenceContainer c = cache.get(wordHash);
        int count;
        if ((c != null) && ((count = c.removeEntries(urlHashes)) > 0)) {
            // removal successful
            if (c.size() == 0) {
                deleteAllReferences(wordHash);
            } else {
                cache.put(wordHash, c);
            }
            return count;
        }
        return 0;
    }
 
    public synchronized void addReferences(final ReferenceContainer container) {
        // this puts the entries into the cache
        int added = 0;
        if ((container == null) || (container.size() == 0)) return;
        assert this.cache != null;
        
        // put new words into cache
        final String wordHash = container.getWordHash();
        ReferenceContainer entries = cache.get(wordHash); // null pointer exception? wordhash != null! must be cache==null
        if (entries == null) {
            entries = container.topLevelClone();
            added = entries.size();
        } else {
            added = entries.putAllRecent(container);
        }
        if (added > 0) {
            cache.put(wordHash, entries);
        }
        entries = null;
        return;
    }

    public synchronized void addEntry(final String wordHash, final ReferenceRow newEntry) {
        assert this.cache != null;
        ReferenceContainer container = cache.get(wordHash);
        if (container == null) container = new ReferenceContainer(wordHash, this.payloadrow, 1);
        container.put(newEntry);
        cache.put(wordHash, container);
    }

    public int minMem() {
        return 0;
    }

}